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Forum Discussion
Random disconnects with CM400 modem
I replaced a 10 year old, burnt out Motorola modem (no connection issues before it died) with a Netgear CM400 back from Best Buy in August 2018. Since then, I've been getting random disconnects. Usually just once a week, but over the past two days it has been up to 5 times an hour (couldn't finish a 5 minute rift in Diablo 3 before losing connection). I just got off the phone with Cox and they said the lines up to my apartment were showing great diagnostic results but the modem was showing loss of sync and connection issues up to 15 times every two hours at varying times over the past three months. Considering the coincidence of connection issues coming up shortly after changing the modem, it seems like there's something wrong on my end. My computer has Windows 10 (ver 1803), is connected to my router (Linksys WRT54G2 V1) by ethernet, the router connects to the modem by ethernet, and everything is connected to a uninterruptible power supply that hasn't shown any power issues since March 2018. I logged into the modem (192.168.100.1) to check the log and found this
| Time | Priority | Description |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 8 22:59:39 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 9 00:00:50 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 00:02:40 2018 | Warning (5) | MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1 |
| Dec 9 00:02:40 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 9 00:35:40 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 01:18:55 2018 | Warning (5) | MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1 |
| Dec 9 01:18:55 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 9 02:06:27 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 02:06:47 2018 | Critical (3) | Ranging Request Retries exhausted |
| Dec 9 02:06:47 2018 | Critical (3) | Unicast Maintenance Ranging attempted - No response - Retries exhausted |
| Dec 9 02:06:47 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 03:58:10 2018 | Critical (3) | Ranging Request Retries exhausted |
| Dec 9 03:58:10 2018 | Critical (3) | Unicast Maintenance Ranging attempted - No response - Retries exhausted |
| Dec 9 03:58:10 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 04:00:05 2018 | Critical (3) | Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out |
| Dec 9 04:00:31 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 04:00:38 2018 | Critical (3) | Unicast Ranging Received Abort Response - initializing MAC |
| Dec 9 04:00:39 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 04:01:03 2018 | Warning (5) | MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1 |
| Dec 9 04:01:03 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 9 04:18:24 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 04:20:39 2018 | Critical (3) | Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out |
| Dec 9 04:21:06 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 04:21:15 2018 | Warning (5) | MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1 |
| Dec 9 04:21:15 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 9 05:00:28 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 05:02:44 2018 | Critical (3) | Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out |
| Dec 9 05:03:11 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 05:03:20 2018 | Warning (5) | MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1 |
| Dec 9 05:03:20 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 9 05:08:34 2018 | Critical (3) | SYNC Timing Synchronization failure - Loss of Sync |
| Dec 9 09:40:11 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 09:40:40 2018 | Critical (3) | Unicast Ranging Received Abort Response - initializing MAC |
| Dec 9 09:40:40 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 09:42:26 2018 | Critical (3) | Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out |
| Dec 9 09:42:52 2018 | Critical (3) | No Ranging Response received - T3 time-out |
| Dec 9 09:43:27 2018 | Warning (5) | MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1 |
| Dec 9 09:43:27 2018 | Notice (6) | TLV-11 - unrecognized OID |
| Dec 9 10:02:47 2018 | Critical (3) | SYNC Timing Synchronization failure - Loss of Sync |
| Dec 9 10:11:48 2018 | Critical (3) |
No Ranging Response received - T3 time-out |
As far as I know, there is no firmware update available for this modem so I'm at a loss as to if the problem is fixable or if I should just get a different modem. Any help would be greatly appreciated.
2 Replies
I did some more research over the past couple days and have made some changes. So, I found the other modem diagnostic page that shows power levels, correctable and uncorrectable errors. With my original setup (50 ft coax cable from the wall to the modem) the power levels on the downstream channels were around -12 to -15 dBmV. After switching my setup around to have the modem and router close to the wall outlet (1.5 ft coax cable, 50 ft ethernet cable to my PC) my downstream power levels are now -3 to -6 dBmV. I haven't had any disconnects for the past two days, but my correcable and uncorrectable errors seem really high:
Downstream Bonded Channels Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables UnCorrectables 1 Locked QAM 256 17 879000000 Hz -5.7 dBmV 34.0 dB 278167 41356 2 Locked QAM 256 18 885000000 Hz -5.2 dBmV 34.0 dB 309215 41345 3 Locked QAM 256 19 891000000 Hz -4.8 dBmV 34.0 dB 343051 59906 4 Locked QAM 256 20 897000000 Hz -5.1 dBmV 34.2 dB 368450 86935 5 Locked QAM 256 21 903000000 Hz -5.2 dBmV 34.2 dB 420998 107528 6 Locked QAM 256 22 909000000 Hz -4.4 dBmV 34.3 dB 557411 122665 7 Locked QAM 256 23 915000000 Hz -3.6 dBmV 34.6 dB 483084 155062 8 Locked QAM 256 24 921000000 Hz -3.9 dBmV 34.4 dB 553903 183524 I did a little math (last modem reset was about 42 hours ago), and that comes out to an average of 79k correcables per hour and 19k uncorrectables per hour over all 8 channels. If I'm understanding this all correctly, the uncorrectable errors are bringing down my effective bandwidth. Could this be due to bad wiring in the apartment? Previously on the phone Cox claimed the lines they had control of showed great diagnostic results.
I also have a CM400 that started going offline intermittently around December. Here in February it slowed so much that I did a speed test and revealed that instead of the 150 I contracted for I was pulling 2 mbps down. I asked the ISP to do a reset of the modem, which they did, trusting that the process would also automatically push any new firmware as I have read. It did not resolve the problem, still 2 mbps. However, I asked them to verify the firmware and they said that it matched the latest version available. They told me to contact Netgear for help. I have been reading that they each blame each other and that Netgear will not help with this issue, so am not pursuing but wanted to share my experience with this otherwise great little modem. Sigh... looks like I will be shopping for a new one.